U.S. patent number 7,528,650 [Application Number 11/591,505] was granted by the patent office on 2009-05-05 for multi-channel digital amplifier, signal processing method thereof, and audio reproducing system having the same.
This patent grant is currently assigned to Samsung Electronics Co., Ltd. Invention is credited to Zhun-woo Kim, Hee-soo Lee, Hae-kwang Park, Young-suk Song.
United States Patent |
7,528,650 |
Song , et al. |
May 5, 2009 |
Multi-channel digital amplifier, signal processing method thereof,
and audio reproducing system having the same
Abstract
A multi-channel digital amplifier system to generate a pulse
width modulation (PWM) signal having a different switching
frequency in each channel, and a signal processing method thereof.
The digital amplifier system includes a PWM conversion unit to
convert a plurality of audio signals on a plurality of channels
into low output power PWM signals having switching frequencies that
are different from each other, a switching circuit unit to amplify
the plurality of low output power PWM signals to a plurality of
high power output PWM signals on the respective channels, and a
filter unit to restore the plurality of high output power PWM
signals to a plurality of analog audio signals on the respective
channels.
Inventors: |
Song; Young-suk (Suwon-si,
KR), Lee; Hee-soo (Suwon-si, KR), Park;
Hae-kwang (Suwon-si, KR), Kim; Zhun-woo (Seoul,
KR) |
Assignee: |
Samsung Electronics Co., Ltd
(Suwon-si, KR)
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Family
ID: |
38284945 |
Appl.
No.: |
11/591,505 |
Filed: |
November 2, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070170983 A1 |
Jul 26, 2007 |
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Foreign Application Priority Data
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Jan 20, 2006 [KR] |
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10-2006-0006290 |
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Current U.S.
Class: |
330/10 |
Current CPC
Class: |
H03F
3/217 (20130101); H03F 3/68 (20130101); H04R
3/12 (20130101); H04S 3/002 (20130101) |
Current International
Class: |
H03F
3/38 (20060101) |
Field of
Search: |
;330/10 ;375/238
;370/212 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2002-111399 |
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Apr 2002 |
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JP |
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2002-92750 |
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Dec 2002 |
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KR |
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2003-15764 |
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Feb 2003 |
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KR |
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Other References
Korean Office Action dated Dec. 12, 2006 issued in KR 2006-6290.
cited by other .
Dutch Search Report dated May 9, 2006 issued in NL 1029619. cited
by other.
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Primary Examiner: Mottola; Steven J
Attorney, Agent or Firm: Stanzione & Kim, LLP
Claims
What is claimed is:
1. A digital amplifier system, comprising: a pulse width modulation
(PWM) conversion unit to convert a plurality of audio signals
received on a plurality of channels into low output power PWM
signals having switching frequencies that are different from each
other; a switching circuit unit to amplify the plurality of low
output power PWM signals on the plurality of channels to a
plurality of high power output PWM signals; and a filter unit to
restore the high output power PWM signals on the respective
channels amplified in the switching circuit unit to a plurality of
analog audio signals on the respective channels.
2. The system of claim 1, wherein the PWM conversion unit
comprises: a PWM control unit to determine frequencies that are
different from each other in the respective channels according to
the number of channels; and a PWM unit to modulate input audio
signals into PWM signals having the different switching frequencies
in the respective channels according to the switching frequencies
determined by the PWM control unit.
3. The system of claim 2, wherein the PWM unit generates the PWM
signals having the switching frequencies that are different from
each other in the respective channels by comparing a level of a
reference high frequency signal set differently for each channel
with a level of the input audio signal in each channel.
4. The system of claim 1, further comprising: a micom unit to
provide channel number information to the PWM conversion unit.
5. The system of claim 1, wherein the switching circuit unit
comprises: a plurality of switching devices to turn on/off the low
output power PWM signals output from the PWM conversion unit, the
switching devices having the switching frequencies that are
different from each other in the respective channels.
6. A digital amplifier usable in an audio reproducing system, the
amplifier comprising: a pulse width modulation conversion unit to
receive information about a plurality of channels and a plurality
of audio data signals on the respective channels, and to generate a
plurality of pulse width modulation (PWM) signals on the respective
channels based on time value comparisons between the plurality of
audio data signals and a plurality of pulse reference signals
associated with the received channel information.
7. The digital amplifier of claim 6, further comprising: a micom
unit to provide the received channel information to the pulse width
modulation conversion unit including the pulse reference signals,
which are preset.
8. The digital amplifier of claim 7, wherein the plurality of pulse
reference signals have frequencies different from each other in the
respective channels.
9. A digital amplifier, comprising: a pulse width modulation (PWM)
conversion unit to receive first and second pulse code modulation
(PCM) signals, to compare time values of the first and second PCM
signals to first and second preset high frequency reference
signals, and to generate first and second pulse width modulation
(PWM) signals based on the respective comparisons.
10. The digital amplifier of claim 9, wherein the first and second
preset high frequency reference signals comprise sawtooth
waves.
11. The digital amplifier of claim 9, wherein the first and second
preset high frequency reference signals have frequencies different
from each other.
12. A method of processing a signal in a digital amplifier system,
the method comprising: determining switching frequencies that are
different from each other for a plurality of channels; converting a
plurality of input audio signals received on the respective
channels into low output power PWM signals having the determined
switching frequencies that are different from each other on the
respective channels; amplifying the low output power PWM signals on
the respective channels to a plurality of high power output PWM
signals; and restoring the amplified high output power PWM signals
on the respective channels to a plurality of analog audio
signals.
13. A method of processing a signal in a digital amplifier system,
the method comprising: receiving information about a plurality of
channels and a plurality of audio data signals on the respective
channels; and generating a plurality of pulse width modulation
(PWM) signal: on the respective channels based on time value
comparisons between the plurality of audio data signals and a
plurality of pulse reference signals associated with the received
channel information.
14. A method of processing a signal in a digital amplifier system,
the method comprising: receiving first and second pulse code
modulation (PCM) signals; comparing time values of the first and
second PCM signals to first and second preset high frequency
reference signals; and generating first and second pulse width
modulation (PWM) signals based on the respective comparisons.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Patent Application
No. 10-2006-0006290, filed on Jan. 20, 2006, in the Korean
Intellectual Property Office, the disclosure of which is
incorporated herein in its entirety by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present general inventive concept relates to a multi-channel
digital amplifier system, and more particularly, to a multi-channel
digital amplifier system to generate a pulse width modulation (PWM)
signal having a different switching frequency in each channel, and
a signal processing method thereof.
2. Description of the Related Art
Generally, a digital amplifier pulse-width modulates a digital
signal with a smaller amplitude, such as a pulse code modulation
(PCM) signal, to generate a PWM signal. The digital amplifier
amplifies the PWM signal to have a large amplitude by using a
semiconductor switching device, such as a field effect transistor
(FET). Then, an audio signal is extracted from the amplified PWM
signal by using a low pass filter.
This digital amplifier may use only a single channel for mono
sound, but in most cases, uses multi channels with two or more
channels, such as 5.1 channels or 7.1 channels.
A conventional multi-channel digital amplifier will now be
explained briefly. FIG. 1 illustrates waveforms of a conventional
pulse width modulation (PWM) signal of the digital amplifier
system. FIG. 2 illustrates waveforms of a conventional
power-amplified PWM signal. First, a number of PWM signals (i.e.,
the number corresponds to a number of channels) are output through
a PWM modulator. These output PWM signals are converted into N high
output power PWM signals by N switching devices, respectively. At
this time, the PWM modulator generates the PWM signals in
respective channels by applying identical switching frequencies to
all channels regardless of the number of channels, as illustrated
in the waveform diagram of FIG. 1. That is, referring to FIG. 1,
the PWM switching frequency of channel A and the PWM switching
frequency of channel B are identical. In this case, the switching
frequency can be determined by rising edges of the PWM Ch A and the
PWM Ch B signals. As can be seen from FIG. 1, the rising edges of
the PWM Ch A and PWM Ch B signals occur at the same point in
time.
Referring to PWM Ch A and PWM Ch B of FIG. 1, although the channels
are different, the identical PWM switching frequencies cause
switching time points in the switching devices to occur at a high
rate. However, if power is turned on or off at the same time at two
or more channels, a power source unit experiences an overload such
that power source noise is generated.
Additionally, as illustrated in FIG. 2, in the actual waveforms of
the PWM signals amplified in the switching devices, a propagation
delay time (t.sub.d1) exists at a time when the switching device is
turned on or off. However, as illustrated in FIG. 2, if the
switching device of channel B is turned on at a time close to the
time when the switching device of channel A is turned on, the
propagation delay time (t.sub.d1) of the switching device increases
or decreases abnormally such that the waveform of the amplified PWM
signal finally output is distorted.
SUMMARY OF THE INVENTION
The present general inventive concept provides a multi-channel
digital amplifier system that reduces crosstalk and noise
components between channels by generating PWM signals in the
respective channels having switching frequencies that are different
from each other.
The present general inventive concept also provides a signal
processing method of generating PWM signals in respective channels
having switching frequencies that are different from each other in
a multi-channel digital amplifier system.
Additional aspects of the present general inventive concept will be
set forth in part in the description which follows and, in part,
will be obvious from the description, or may be learned by practice
of the general inventive concept.
The foregoing and/or other aspects of the present general inventive
concept are achieved by providing a digital amplifier system
including a pulse code modulation (PWM) conversion unit to convert
a plurality of audio signals into low output power PWM signals
having switching frequencies that are different from each other, a
switching circuit unit to amplify the plurality of low output power
PWM signals to a plurality of high power output PWM signals on the
respective channels, and a filter unit to restore the plurality of
high output power PWM signals to a plurality of analog audio
signals on the respective channels.
The foregoing and/or other aspects of the present general inventive
concept are also achieved by providing a digital amplifier,
including a pulse width modulation (PWM) conversion unit to receive
pulse code modulation (PCM) audio data for a plurality of channels
and to convert the PCM audio data into corresponding pulse width
modulation (PWM) signals having different frequencies.
The foregoing and/or other aspects of the present general inventive
concept are also achieved by providing a digital amplifier usable
in an audio reproducing system, the amplifier including a pulse
width modulation conversion unit to receive information about a
plurality of channels and a plurality of audio data signals on the
respective channels, and to generate a plurality of PWM signals on
the respective channels based on time value comparisons between the
plurality of audio data signals and a plurality of pulse reference
signals associated with the received channel information.
The foregoing and/or other aspects of the present general inventive
concept are also achieved by providing a digital amplifier,
including a PWM conversion unit to receive first and second pulse
code modulation (PCM) signals, to compare time values of the first
and second PCM signals to first and second preset high frequency
reference signals, and to generate first and second pulse width
modulation (PWM) signals based on the respective comparisons.
The foregoing and/or other aspects of the present general inventive
concept are also achieved by providing an audio reproducing system,
the system including a digital amplifier having a pulse width
modulation (PWM) conversion unit to receive pulse code modulation
(PCM) audio data for a plurality of channels and to convert the PCM
audio data into corresponding pulse width modulation (PWM) signals
having different frequencies, and a plurality of output units to
output a plurality of analog audio signals derived from the PWM
signals of the respective channels.
The foregoing and/or other aspects of the present general inventive
concept are also achieved by providing a method of processing a
signal in a digital amplifier system, the method including
determining switching frequencies that are different from each
other in a plurality of channels, converting a plurality of input
audio signals into low output power PWM signals having the
determined switching frequencies that are different from each other
on the respective channels, amplifying the plurality of the
generated low output power PWM signals to a plurality of high power
output PWM signals in the respective channels, and restoring the
plurality of the amplified high output power PWM signals to a
plurality of analog audio signals in the respective channels.
BRIEF DESCRIPTION OF THE DRAWINGS
These and/or other aspects of the present general inventive concept
will become apparent and more readily appreciated from the
following description of the embodiments, taken in conjunction with
the accompanying drawings of which:
FIG. 1 illustrates waveforms of a conventional pulse width
modulation (PWM) signal of a conventional digital amplifier;
FIG. 2 illustrates waveforms of a conventional power-amplified PWM
signal;
FIG. 3 is a block diagram illustrating a multi-channel digital
amplifier system according to an embodiment of the present general
inventive concept;
FIG. 4 illustrates operational waveforms of a PWM conversion unit
of the multi-channel digital amplifier system of FIG. 3;
FIG. 5 illustrates waveforms of a PWM signal amplified in a
switching circuit unit of the multi-channel digital amplifier
system of FIG. 3;
FIG. 6 is a diagram illustrating a switching circuit unit according
to an embodiment of the present general inventive concept; and
FIG. 7 is a flowchart illustrating a method of processing a signal
of a digital amplifier according to an embodiment of the present
general inventive concept.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference will now be made in detail to the embodiments of the
present general inventive concept, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to the like elements throughout. The embodiments are
described below in order to explain the present general inventive
concept by referring to the figures.
FIG. 3 is a block diagram illustrating a multi-channel digital
amplifier system according to an embodiment of the present general
inventive concept
The digital amplifier system of FIG. 3 includes a PWM conversion
unit 310, a micom (microcomputer) unit 320, a switching circuit
unit 330, a power supply unit 340, and a low pass filter (LPF) unit
350. The PWM conversion unit 310 includes a PWM control unit 312
and a PWM unit 314. The switching circuit unit 330 includes a
plurality of switching devices corresponding to multiple
channels.
First, an input analog audio signal is converted into pulse code
modulation (PCM) audio data by a digital signal processor (DSP)
(not illustrated).
The micom unit 320 generates control signals to control blocks
and/or components of the multi-channel digital amplifier system,
such as function control and initialization. Additionally, the
micom unit 320 provides channel information of the system, such as
a number of channels, to the PWM control unit 312.
According to the channel number information provided by the micom
unit 320, the PWM conversion unit 310 converts input PCM audio data
into low output power PWM signals having different switching
frequencies.
More specifically, in the PWM conversion unit 310, the PWM control
unit 312 determines PWM switching frequencies that are different
from each other in the respective channels according to the channel
number information received from the micom unit 320. For example,
if the number of the channels is determined to be two, the PWM
control unit 312 may determine a switching frequency of channel A
as 384 KHz and a switching frequency of channel B as 432 KHz.
According to the PWM switching frequencies determined for the
respective channels by the PWM control unit 312, the PWM unit 314
may convert the input PCM audio data into the PWM signals by using
an ordinary digital amplification PCM technique. In the present
embodiment, if the switching frequency information of each channel
is input from the PWM control unit 312, the PWM unit 314 compares a
level of the input audio signals in each channel with a level of a
reference high frequency signal set differently for each channel.
Based on this comparison, the PWM unit 314 generates the PWM
signals in the respective channels having the switching frequencies
that are different from each other.
The power supply unit 340 provides operational power to the
switching devices for the respective channels in the switching
circuit unit 330.
The switching circuit unit 330 power-amplifies low output power PWM
signals of the N channels, which are converted by the PWM
conversion unit 310, to high output power PWM signals with power
provided by the power supply unit 340. For example, the switching
circuit unit 330 may amplify about 3.3V low output power PWM
signals to between 5V and 40V high output power PWM signals.
The LPF unit 350 low-pass filters each of the N channel signals
using inductors (L) and capacitors (C). By removing high frequency
components of the high output power PWM signals in the N channels
amplified by the switching circuit unit 330, the LPF unit 350
restores N channel analog audio signals.
Finally, the audio signals of the respective channels restored by
the LPF unit 350 are output to speakers 360-1 through 360-n, which
correspond to the respective N channels.
FIG. 4 illustrates operational waveforms of the PWM conversion unit
310 of FIG. 3.
Referring to FIG. 4, the PWM signals in channel A and channel B are
generated to have different frequencies (f.sub.SA) and (f.sub.SB),
respectively, by using preset reference high frequency signals. The
different frequencies (f.sub.SA) and (f.sub.SB) can be determined
in FIG. 4 by the respective rising edges of the PWM signals. The
PCM signal of channel A 420-1 is converted into a PWM signal (i.e.,
PWM Ch A) by using a first reference high frequency signal 410-1,
and the PCM signal of channel B 420-2 is converted into a PWM
signal (i.e., PWM Ch B) by using a second reference high frequency
signal 410-2. That is, the first reference high frequency signal
410-1 is compared with the level of the input PCM signal 420-1. If
the PCM signal 420-1 is greater than the first reference high
frequency signal 410-1, a high logic level is output. If the PCM
signal 420-1 is less than the first reference high frequency signal
410-1, a low logic level (1) is output. Also, the second reference
high frequency signal 410-2 is compared with the level of the input
PCM signal 420-2. If the PCM signal 420-2 is greater than the
second reference high frequency signal 410-2, a high logic level is
output. If the PCM signal 420-2 is less than the second reference
high frequency signal 410-2, a low logic level is output.
Accordingly, the PWM conversion unit 310 generates the switching
frequency (f.sub.SA) of the PWM signal of channel A and the
switching frequency (f.sub.SB) of the PWM signal of channel B such
that the switching frequencies are different from each other.
FIG. 5 illustrates waveforms of a PWM signal output from the PWM
conversion unit 310 of FIG. 3.
FIG. 5 illustrates the actual waveforms of PWM signals having the
different switching frequencies with respect to the channels A and
B. A propagation delay time (t.sub.d2) exists between the PWM
signals on the channels A and B. Referring to FIG. 5, if the
switching frequencies of the respective channels are different, a
time when the switching device (i.e., of the switching circuit unit
330) of the channel A is turned on is different from a time when
the switching device (i.e., of the switching circuit unit 330) of
the channel B is turned on such that an abnormally rapid increase
or decrease in the propagation delay time (t.sub.d2) of a switching
device does not occur. In FIG. 5, (t.sub.SA) indicates a period of
the PWM signal on channel A, and (t.sub.SB) indicates a period of
the PWM signal on channel B.
FIG. 6 is a diagram illustrating the switching circuit unit 330 of
FIG. 3 according to an embodiment of the present general inventive
concept.
In each channel of the switching circuit unit 330 a switching
device including a PMOS transistor (P1) and an NMOS transistor (N1)
is disposed in parallel. For example, in one channel, the PMOS
transistor (P1) having a power source voltage (+V) connected to a
source terminal thereof is switched according to a first channel
PWM signal (PWM Ch1) of the PWM conversion unit 310. Also, the NMOS
transistor (N1) having a drain terminal thereof connected to a
drain terminal of the PMOS transistor (P1) and a source terminal
connected to a ground voltage (-V) is switched according to the
first channel PWM signal (PWM Ch1). Here, +V and -V are voltages
supplied from a voltage source (e.g., the power supply unit 340).
Also, R1 and R2 are resistances disposed in a conductor that
connects the voltage source and the switching transistors.
FIG. 7 is a flowchart illustrating a method of processing a signal
of a digital amplifier according to an embodiment of the present
general inventive concept. The method of FIG. 7 may be performed by
the system of FIG. 3. Accordingly, for illustration purposes, the
method of FIG. 7 is described below with reference to FIGS. 3 to
6.
First, according to a number of channels, PWM switching frequencies
in the respective channels that are different from each other are
determined in operation 710.
Then, switching frequency information that are different from each
other in the respective channels are transferred to the PWM unit
314 in operation 720.
By applying the switching frequencies set in the respective
channels to a plurality of input audio signals, the audio signals
are converted into PWM signals having different switching
frequencies in operation 730.
Then, by applying the PWM signals to the switching circuit unit
330, the low output power PWM signals of the plurality of channels
are amplified to generate the high output PWM signals in operation
740.
Finally, the amplified high output power PWM signals of the
plurality of channels are restored to a plurality of analog audio
channel signals.
The present general inventive concept can be embodied as computer
readable codes on a computer readable recording medium. The
computer readable recording medium is any data storage device that
can store data which can be thereafter read by a computer system.
Examples of the computer readable recording medium include
read-only memory (ROM), random-access memory (RAM), CD-ROMs,
magnetic tapes, floppy disks, optical data storage devices, and
carrier waves (such as data transmission through the Internet). The
computer readable recording medium can also be distributed over
network coupled computer systems so that the computer readable code
is stored and executed in a distributed fashion.
According to the various embodiments of the present general
inventive concept as described above, PWM signals having different
switching frequencies in respective channels are used in a
multi-channel digital amplifier system, such as a 5.1-channel or
7.1-channel system. Accordingly, a case in which switching devices
in two or more channels are turned on at the same time occurs much
less frequently such that crosstalk between channels can be
reduced. Also, since a harmonic component of the switching
frequency occurring in each channel is different from each other, a
characteristic of electromagnetic interference can be reduced.
Although a few embodiments of the present general inventive concept
have been shown and described, it will be appreciated by those
skilled in the art that changes may be made in these embodiments
without departing from the principles and spirit of the general
inventive concept, the scope of which is defined in the appended
claims and their equivalents.
* * * * *